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Effects of galactic interaction on the star formation efficiency and the diffuse gas
Neven Tomičić (INAF-OaPD)
INAF-OaPD: Daniela Bettoni, Marco Gullieuszik, Andrea Franchetto, Alessia Moretti, Bianca Poggianti, Benedetta Vulcani, ...
Kathryn Kreckel (MPIA), I-Ting Ho (MPIA), Eva Schinnerer (MPIA), Guillermo A. Blanc (Carnegie), Chris Faesi (MPIA), Santiago Garcia-Burillo (OAN), Brent Groves (ANU), Annie Hughes (CNRS, IRAP), Tom Jarret (Uni. Cape Town), Maria Kapala (Uni. Cape Town), Adam Leroy
(OSU), Rebecca McElroy (MPIA), Jerome Pety (IRAM), Miguel Querejeta (ESO), Florent Renaud (Lund Uni.), Toshiki Saito (MPIA), Karin Sandstrom (UCL), David Thilker (Johns Hopkins Uni.)
1) Star Formation Efficiency (SFE*) in interacting galaxies
SFE = 1/τdepletion =ΣSFR /Σgas
2) Effects of Diffuse emission
Star Formation Rate (SFR)
How does galactic interaction affects efficiency of SFR?
SFE = 1/τdepletion =ΣSFR /Σgas
1) Does SFE change through galactic evolution and interaction?
2) Mean galactic value vs. sub-galactic values?
τdepletion
≈ 2 Gyr
How does galactic interaction affects efficiency of SFR?
SFE = 1/τdepletion =ΣSFR /Σgas
1) Does SFE change through galactic evolution and interaction?
2) Mean galactic value vs. sub-galactic values?
τdepletion
≈ 2 Gyr
Fig: The Kennicut-Schmidt diagram of a pair of simulated interacting galaxies.
Credit: Renaud et al. 2014
Is molecular gas also assymetric?
NGC 2276:Asymmetric SFRsurface density
Asymmetric SFR
surface density
Symmetric molecular gas
surface density
Fig. Surface density of the SFR and the molecular gas, and the depletion
time of NGC 2276. Credit: Tomičić+18
Slit
Ram pressure?
Tidal force?
Fig. Kennicutt-Schmidt diagram of NGC 2276. Credit: Klaas et al. 2016; Saito et al. 2015,16; Tomičić+18
Extragalactic forces?
1) Spatial variation in SFE
2) Mean galactic valuevs.
3 orders of magnitude variation in SFE
3) Galactic evolution?
Slit
Ram pressure?
Tidal force?
Fig. Kennicutt-Schmidt diagram of NGC 2276. Credit: Klaas et al. 2016; Saito et al. 2015,16; Tomičić+18
Extragalactic forces?
1) Spatial variation in SFE
2) Mean galactic valuevs.
3 orders of magnitude variation in SFE
3) Galactic evolution?
Disk
Star Formation Efficency in the tails of stripped galaxies
(GASP survey)?
See the talk of A. Moretti
JO206
MUSE, VLT (ESO, Chile)
Diffuse ionised gas in tails
- fractions- effects on SFR and Metallicity- origin?
Fig: Jellyfish galaxy JW100, Hα,corr (B. Poggianti et al. 2017) and stellar disk (M. Gullieuszik et al. 2019).
Work in progress
Stellar
disk
M. GullieuszikB. Poggianti
Diffuse Ionised Medium (DIG)
Fig: Composite Hα intensity map; c. Finkbeiner+2003
Warm low density
Higher [SII]/Hα ratio
kpc scales (!!)
Sources: - HII regions- SN remnants- stellar winds - clumpy (fractal) ISM- scattering from the dust- CR
HII
DIG
Methods of quantifying:
Fig: Jellyfish galaxy JO206, Hα image with knots (HII regions) determined by Hα flux.
c. Poggianti+2016
Fig. Boundaries of HII regions determined the [SII]/Hα ratio.
c. Kreckel+2016
1) Hα flux 2) [SII]/Hα ratio
HII HII
DIGDIG
[SII]/Hα > 0.2
[SII]/Hα = 0.1
Metallicity?100%
0%
3) [SII]/Hα vs Hα,corr diagram
Fig: [SII]/Hα vs Hα,corr diagram to determine the fraction of the DIG.
c. Blanc+2009
DIG fraction
Non-Jellyfish galaxies.
Fig: Fitting [SII]/Hα vs Hα,corr diagram to determine the fraction of the DIG. Left- data corrected for gas metallicity variation (c. A. Franchetto). Right- observed [SII]/Hα values, with lines of the fit varied by gas metallicities.
c. Tomicic+in prep.
A. Franchetto
Fig: Left- Hα,corr map with HII knots. Right- estimated DIG fraction.c. Tomicic+in prep.
Non-Jellyfish galaxies.
How reliable are methods that use only the [SII]/Hα ratio or using only the Hα emission?
Next steps:
- How different Tails from Disks are?- Fraction of DIG among the Jellyfish galaxies- origin of the DIG?
Thank you!
Fig: Stellar mass distribution (color) and
observed Hα (contours). Credit: Tomičić+18
Ram pressureTidal force
Fig: Stellar mass distribution (color) and observed Hα (contours).
Credit: Tomičić+18
Fig: Proxy for an age of the stellar clusters. Credit: Tomičić+18